Managed to figure it out on my own. I'll still share the solution here as a reply in case any other amateur Craft Tweaker users run into the same issue. Specifically, the sample code from the futurepack github is actually missing vital characters.
Example from the website on how to remove an assembly table recipe:
What you actually need to type to remove an assembly table recipe:
mods.futurepack.assembly.remove([<input1>, <input2>, <input3>]);
Notice how the example completely leaves out the fact that you need to put in ALL THREE ingredients for the recipe, and that these need to also be bound inside of square brackets. The example also leaves out the vital semicolon at the end of the line.
Without the square brackets, the recipe removal fails but the rest of the script runs fine. Without the semicolon on the end, the whole script breaks.
I hope this helps anyone who comes across it!